An improved method for quantitative determination of bromate in bread and fish paste products was established.
A sample was homogenized with distilled water and made up to 200ml after centrifugation. The supernatant was filtered and n-butanol-ethanol (2:1) mixture was added to 10ml of the filtrate. The mixture was allowed to stand for 10min then centrifuged to remove the precipitate. DEAE-Sephadex A-25 suspension and acetic acid were added to the supernatant, and the mixture was stirred for 5min. After centrifugation, the supernatant was subjected to the same procedure with DEAE-Sephadex A-25 suspension. The DEAE-Sephadex A-25 was mixed with ethanol, and rinsed twice with ethanol, 5.0% acetic acid and distilled water. The solid was packed in a chromatocolumn, and bromate was eluted with 30ml of 30% potassium chloride solution. Two ml of 4×10^-3M styrene monomer solution (washed with 1% sodium hydroxide solution before use), 1ml of 0.01M potassium bromide solution and 1ml of sulfuric acid were added to the effluent, and the whole was shaken vigorously. Styrene bromo derivative was extracted with 2ml of n-hexane, and bromate was determined by ECD-GC.
In this method, it was found that bromate in foods could be determined with a recovery of 80-92.3% and a variation coefficient of 6.2-2.6%. The detection limit was 0.01μg/g.